Various types of conveyors have been used for centuries for moving goods. Belt, chain, roller, and screw-type conveyors each have their advantages. In recent years, various industries have increasingly used conveyors having an elongate tray which is cyclically powered by a drive motor to move goods along the tray. One type of conveyor using such a tray is a vibratory conveyor, as disclosed in U.S. Pat. No. 5,211,277. The cycle of a vibratory conveyor tray thrusts the goods forward and upward, then pulls the tray backward while the goods are suspended in the air. The stroke of a vibratory conveyor is generally less than 1/8th inch, and typically is about 1/16th inch. A vibratory conveyor has the benefit of simplicity and easy cleaning, since only the conveyor tray contacts the material being conveyed. Accordingly, vibratory conveyors are commonly used in the food processing industry.
Another type of cyclically powered conveyor which benefits from the use of an elongate tray is a linear motion conveyor. In a linear motion conveyor, the drive motor moves the tray forward to convey goods supported on the tray, and then pulls the tray rearward at a faster rate so that the goods slide along the conveyor tray, thereby effectively transporting the goods along the conveyor tray. The stroke of a linear motion conveyor is generally from 1 inch to 2 inches, and typically from 11/2 inches to 2 inches. A linear motion conveyor has several significant advantages over a vibratory conveyor, primarily because the tray motion is more gentle on the transported goods. Linear motion conveyors are well suited for transporting fragile goods, such as snack foods, since the goods may be reliably transported along the conveyor tray without being damaged. Since the goods are not thrust upward off the tray supporting surface, seasonings or other particles loosely attached to the goods remain on the goods much better than when using a vibratory conveyor. A linear motion conveyor is disclosed in U.S. Pat. No. 5,351,807.
In many applications, goods being moved along a conveyor tray must be temporarily stored. Upstream processing equipment, for example, continuously produces snack foods, and conveyors conventionally transport these goods to downstream seasoning equipment or bagging equipment. For various reasons, the downstream equipment may be temporarily shut down, e.g., to clean jams or to replace packaging. Since the upstream equipment preferably continues to output goods, a buffer or accumulator system is required to temporarily store goods while operation of the downstream equipment is temporarily discontinued.
Traditional accumulator systems include belt conveyors which are moved under the discharge of the conveyor tray. The belt is slowly powered to transport the goods away from the conveyor tray. Hopefully the operation of the downstream equipment will be resumed before the goods reach the discharge end of the belt conveyor. Once operation of the downstream equipment resumes, the belt conveyor may be reversed to feed the stored goods back into the conventional conveyor system. Belt-type accumulators take up considerable space and are expensive to purchase and maintain. Belt-type conveyors also do not have the advantages of a conveyor which moves goods along a unitary tray, and accordingly sanitation costs are typically quite high.
Another type of accumulator system which has been used with vibratory conveyors may be referred to as an on-demand system. An on-demand system slows down the product travel speed along the conveyor tray to compact the product and thereby gain buffer capacity. This on-demand system typically causes increased damage to the product, in part because the vibrating discharge end of one conveyor may engage built up product accumulated on a downstream conveyor. This type of on-demand system generally cannot be successfully used with a linear motion conveyor because of the much longer stroke length of the linear motion conveyor, which would cause even more damage to the goods. Those skilled in the art appreciate that the product damage caused by approximately 1/16th inch stroke of the discharge end of an on demand vibratory conveyor might be acceptable for some applications, but that the corresponding product damage caused by the 11/2 inch stroke of linear motion conveyor engaging the built-up product would be unacceptable.
Accordingly, an improved accumulator system is required for conveyors, and particularly for conveyors with a cyclically powered tray, such as vibratory and linear motion conveyors. A preferred accumulator system would be relatively inexpensive and would utilize existing conveyor equipment, thereby reducing installation and maintenance costs. A preferred accumulator system also would require little floor space, since floor space in many applications is at a premium, particularly when the accumulator system is installed for an existing conveyor system. Because conveyors which utilize a unitary tray commonly transport fragile products, the accumulator system preferably is also gentle on the goods and results in minimal damage to the accumulated product. In many applications, the transported product itself has a relatively short shelf life, and accordingly the accumulator system preferably is a first in/first out system, so that the goods first added to the accumulator system are the first goods to pass from the accumulator system to downstream equipment.
The disadvantages of the prior art are overcome by the present invention, and an improved in-line conveyor with an accumulator system and method are hereinafter disclosed for temporarily storing products conveyed along a cyclically powered conveyor tray.